This invention relates to a CDMA (code division multiple access) base station transmission device and a method for conducting the spread multiplex transmission in a CDMA base station transmission device.
In conventional CDMA base station transmission devices, transmit data is spread by spread code to each user for each symbol, as unit data of each user, then multiplex-synthesized by the number of users. D/A converted for each antenna used to transmit it, modulated into radio frequency band, then transmitted. Here, the unit to be spread-multiplexed is each antenna. Therefore, it is necessary to provide a spread multiplex circuit for each antenna. When the spread multiplex circuit is provided for each antenna, the circuit needs to be composed so that transmit data corresponding to all supposed users as the input end of the spread multiplex circuit can be input.
FIG. 1 shows a case of conducting the spread multiplex transmission for data of L users selected from transmit data of N users. In this case, transmit data 110 (1) to 110 (N) of the N users are input to a user selection part 111 in a spread multiplex synthesis unit 101, where transmit data corresponding to the number of users to be transmitted by a transmitting antenna 105 are selected. In FIG. 1, data of L users (Nxe2x89xa7L) are selected. The user transmit data selected are input to spread modulation parts 112 (1) to 112 (L), where the spreading is conducted. The spreading is done by a spreading part 116 using spread codes generated from a spread code generation part 115. Signals of L users after the spreading are synthesized by a multiplex synthesis part 113, then D/A converted by a D/A converter 103. The D/A converted spread multiplex signal of L users is modulated into radio frequency band by an orthogonal modulation part 104, then transmitted through the transmission antenna 105.
FIGS. 2 and 3 each show circuit compositions in a case that the number of users to be transmitted in FIG. 1 increases by that of M users (Mxe2x89xa7L) from N users. In FIG. 2, when the number of users transmitted increases by M, the user selection part 111 in the spread multiplex synthesis unit 101 is altered, thereby data of L users are selected from those of (N+M) users, and are input to the spread modulation parts 112 (1) to 112 (L). In this case, the maximum multiplex number to be transmitted through the transmission antenna 105 is L, the same as the case in FIG. 1. It is impossible to select the number of users more than L from the (N+M) users and to spread-multiplex them.
In contrast with this, in FIG. 3, when the number of users transmitted increases by M, a spread multiplex synthesis unit 102 for spread-multiplexing selecting by L users from the M users is added, other than the spread multiplex synthesis unit 101 for spread-multiplexing selecting by L users from the N users in FIG. 1. The outputs of these two spread multiplex synthesis units are multiplexed by an additional multiplex synthesis part 114. Thus, in this case, the spread synthesis multiplexing of (2xc3x97L) users at the maximum can be conducted, but the additional multiplex synthesis part 114 is required. Also, this multiplex synthesis part needs to be provided with a composition independent of the spread multiplex synthesis unit for each unit of antenna, therefore causing an increase in circuit part for each unit of antenna.
Accordingly, it is an object of the invention to provide a CDMA base station transmission device that, even when the number of users increases, an increase in the scale of circuit part dependent on each unit of antenna can be suppressed and the device adaptable can be composed easily by the addition of spread multiplex synthesis unit.
According to the invention, a CDMA base station transmission device for spreading transmit data by spread code to each user for each symbol as unit data of each user, multiplex-synthesizing the spread data by the number of users, D/A-converting the multiplexed data, modulating the D/A-converted data into radio frequency band, then transmitting the modulated data through an antenna, comprises:
a first spread multiplex synthesis unit that spreads and multiplexes transmit data of a predetermined number of users to be selected from a plurality of users; and
a second spread multiplex synthesis unit that is additionally provided when the number of users increases and that spreads and multiplexes transmit data of a predetermined number of users to be selected from a plurality of users;
wherein the first spread multiplex synthesis unit is provided with a first multiplex synthesis part inside the unit, and the first multiplex synthesis part adds the spread-multiplexed data of the first spread multiplex synthesis unit and the spread-multiplexed data of the second spread multiplex synthesis unit, D/A-converts the added spread-multiplexed data, modulates it into radio frequency band, transmits it through the antenna.
According to another aspect of the invention, a method for conducting the spread multiplex transmission in a CDMA base station transmission device, comprises the steps of:
in a first multiplex synthesis part for spreading transmit data by spread code to each user for each symbol as unit data of each user, multiplex-synthesizing the spread data by the number of users, adding the spread-multiplexed data of the first spread multiplex synthesis unit and the spread-multiplexed data of a second spread multiplex synthesis unit that is additionally provided;
D/A-converting the added spread-multiplexed data;
modulating the D/A-converted data into radio frequency band; and
transmitting the modulated data through an antenna.
According to another aspect of the invention, a method for conducting the spread multiplex transmission in a CDMA base station transmission device, comprises the steps of:
in a first spread multiplex synthesis unit for spreading transmit data by spread code to each user for each symbol as unit data of each user, multiplex-synthesizing the spread data by the number of users, adding the spread-multiplexed data of the first spread multiplex synthesis unit and the spread-multiplexed data of a second spread multiplex synthesis unit that is additionally provided;
in the second spread multiplex synthesis unit, adding the spread multiplexed data of the first spread multiplex synthesis unit and the spread-multiplexed data of the second spread multiplex synthesis unit;
D/A-converting the added spread-multiplexed data for each antenna;
modulating the D/A-converted data into radio frequency band; and
transmitting the modulated data through the antenna.
In this invention, the spread multiplex synthesis unit is, inside the unit, provided with a function for adding the multiplexed data from another spread multiplex synthesis unit to its multiplexed data and a function for controlling the addition of the multiplexed data. So, even when the number of users to be transmitted increases, with the additionally-provided spread multiplex synthesis unit, the spread-multiplexing of data of the increased users can be conducted and the spread-multiplexed data can be added to the spread-multiplexed data of the other spread multiplex synthesis unit. Therefore, an increase in the scale of circuit part dependent on each unit of antenna can be suppressed and the device adaptable can be composed easily by the addition of spread multiplex synthesis unit.